Decreasing the forming time in gas blow forming using fine grained Mg alloy AZ31B thin sheet with a thickness of 0.6 mm was studied in this work. Tensile tests and gas blow forming using stepwise pressurisation profiles were performed to explore the deformation behaviour of a fine grained AZ31B Mg alloy sheet. The alloy sheets were successfully deformed into hemispherical domes using two proposed stepwise pressurisation profiles during gas blow forming. As a result, significant reduction in forming time was achieved. Maximum effective deformation rates of 1.02 x 10(-2) and 1.98 x 10(-2) s(-1) were obtained at 300 and 370 degrees C respectively. It was feasible to form a hemispherical dome with a height of 20 mm in less than 80 s at 370 degrees C. The results confirmed that the thickness distribution along the centreline of the formed dome was sensitive to the pressurisation profiles. A higher thinning effect was observed at 370 degrees C due to the higher deformation rate imposed during forming. Grain growth was not a serious problem for forming even at 370 degrees C, and static grain growth should be the major factor resulting in grain growth during forming.